Various work tools have been used to carry out operations on workpieces that travel along conveyors. Commonly the work tool may be supported for movement relative to the workpiece, transversely and/or longitudinally relative to the direction of movement of the conveyor. U.S. Pat. Nos. 5,243,886 and 5,365,816 disclose nozzles that emit very high-speed water jets to cut foods and other objects that are carried by an underlying conveyor belt. The nozzles are mounted on carriages that ride along tracks disposed transversely to the moving conveyor. By timing the transverse movement of the carriages, it is possible to make cuts in the workpiece that are diagonal to the direction of movement of the conveyor and also it is possible to make curved cuts in the workpiece.
However, it is desirable to be able to move the nozzle in the direction longitudinally of the conveyor so as to achieve higher cutting speeds and/or more complicated cutting patterns while maintaining high precision. To date, this effort has been hampered by the inability to move and change the direction of movement of the nozzle as quickly as desirable, due at least in part to the relatively high mass of the carriage and related apparatus employed to mount and move the working tool. For instance, U.S. Pat. Nos. 4,204,448 and 4,882,961 disclose gantry systems for water jet cutters employing a support structure that spans transversely across an underlying conveyor. The transverse support structure rides on longitudinal tracks extending along the sides of the conveyor. A work tool-supporting carriage is carried and guided by the transverse structure. The transverse structure also carries a drive system for moving the carriage along the support structure, back and forth across the path of the conveyor. These structures for carrying and moving the water jet nozzle comprise considerable mass that limits the speed at which the water jet cutter nozzles may be moved, particularly in the direction parallel to the direction of movement of the conveyor.
U.S. Pat. No. 5,402,691 discloses a gantry apparatus similar to that disclosed in U.S. Pat. Nos. 4,204,448 and 4,882,961, but not adapted to be used with workpieces that move on an underlying conveyor. The '691 patent utilizes a typical "H" support structure having a pair of spaced apart, parallel members that span across the workpiece. A longitudinally disposed "Y" support member extends transversely to the parallel members of the "H" support structure. A tool mounting structure moves along the length of the "Y" member under the operation of a drive system, including a drive motor, carried by the Y member, thus adding significantly to the total mass that must be moved when moving the work tool.
The present invention addresses the foregoing and other drawbacks of prior art apparatuses for high-speed bi-directional movement of water jet nozzles and other work tools.